Method for dynamically refining and deodorizing fats and oils by distillation

ABSTRACT

A method and apparatus for distilling, especially vacuum refining and deodorizing edible oils and fats utilizing sheets of oil driven downwardly in a distiller with a vacuum source at its top. A nozzle includes pressure equalization chambers, cantilever adjustment screws, and a central drag sheet to produce longer lasting and more uniform thin oil sheets to be driven in the distiller. A continuous process deaerates, dehydrates, degums, bleaches, refines, removes tocopherol, deodorizes, and strips peroxides and hydroperoxides from raw oil in a series of isothermal stages utilizing driven sheet distillers. No stripping steam is used except in the stage which strips peroxides and hydro peroxides. The method produces valuable, pure products such as tocopherol and fractionated fatty acids. It is especially efficient in heat exchange and low in waste and pollution producing products. A steam sparging nozzle for distributing steam in the stripping of peroxides and hydroperoxides includes a plurality of small tubes with openings which restrict steam flow so as to produce a uniform distribution of optimum size steam bubbles in the steam stripping column of oil. A microwave excitation device radiates the oil immediately prior to forming the driven sheets to excite the more volatile components of the oil for distilling.

This is a divisional of copending application Ser. No. 07/170,110 filedon Mar. 11, 1988, now abandoned which is a continuation of applicationSer. No. 835,278 filed on Apr. 25, 1986 now abandoned which was adivision of Ser. No. 540,037 filed on Oct. 17, 1983 now U.S. Pat.4,613,410.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates in general to methods and apparatus for refiningand deodorizing edible oils and fats and particularly to methods andapparatus for continuous vacuum refining and deodorizing of fats andoils.

2. Description of the Prior Art

In the process of refining either vegetable or animal fats and oils toprepare foods such as margarine and cooking oils, several processes arepresently available. Generally, these processes utilize vacuumdistillation to remove odoriferous substances such as free fatty acidsfrom the oils and fats comprising mainly triglycerides. By this means,the oils and fats are made more palatable and their odors and tastes areimproved.

While the odoriferous and taste giving materials are more volatile thanthe oils in which they are found, the oils and fats may not be subjectedto relatively high temperatures since undesirable polymerization orproduction of additional fatty acids, alcohols, aldehydes, etc., fromthe fats and oils occur at higher temperatures. Accordingly, thepreferred method of deodorizing fats and oils has been by means of avacuum distillation allowing a lower temperature removal of these morevolatile odoriferous substances. Most of these vacuum processes use astripping agent such as steam to increase the surface area of liquid oiland fat, to provide a carrying medium for removal of the volatilesubstances and to react with and strip certain undesirable components.In vacuum steam stripping, the oils are contacted by steam percolatingupwardly in columns or trays of oil at elevated temperatures andsubatmospheric pressures.

Many prior art processes of deodorization are discontinuous; i.e. theprocesses are performed in discrete stages, each completed before thenext stage begins. For example, a batch of oil might be degummed anddeaerated, then stored before further refining and deodorizing. Oils andfats may also be blended after refining and storage to be subsequentlydeodorized as a single product.

The first step of the prior art is the removal of water solublephosphatides, or more particularly, lecithins. The process is known asdegumming. The oil is washed with a mixture of water and acid, usuallyphosphoric, citric or malic (the water and acid is approximately 4% ofthe weight of the oil) in blenders, high speed mixers and subsequentlycentrifuged, discharging the phosphatides with the water. As thestability of the oil has been protected by the presence of thelecithins, the oil should be immediately deaerated and dehydratedthrough contact equipment operating at approximately 150° F. to 175° F.at reduced pressures.

Another step of the prior art is bleaching. Bleaching is the removal ofundesirable color from the oil, generally by the use of clays capable ofabsorbing the color ingredients upon its surface. The mixture of oil andclay is then separated in pressure filters leaving the oil free of theobjectionable color. This step is usually performed separately from theother steps.

Following degumming, deaeration, dehydration and bleaching the oil isrefined and deodorized. If the oil is a normal vegetable oil, not cottonseed oil, and has not been abused in extraction, transportation orstorage, it will contain, at this point, approximately 0.5% removablehydrocarbons with the balance being pure triglycerides. Not accountingfor trace materials, the 0.5% will contain about 85% free fatty acidsand 15% tocopherol.

Two methods of refining are commonly used: caustic and steam. Causticrefining reacts the free fatty acids with caustic, saponifying the freefatty acid for removal. Steam refining recognizes that most of the freefatty acids are subject to normal distillation and the method uses steamto spring and carry the distillates from the oil. Because of temperatureconstraints, the latter method must be vacuum stripping anddistillation.

For batch type deodorization, the equipment most frequently used forsteam stripping deodorization of edible oils, not including deaeration,has been a singular column with a singular vacuum source placed on topof the column. The most common vacuum system is a multiple effect orstaged steam eductor system. Oil is retained in the column or recycledthrough the column while stripping steam is bubbled up through thecolumn for stripping free fatty acids or other odoriferous materialsfrom the oil. The overhead from the column is a mixture of eductorsteam, stripping steam, tocopherol, free fatty acids and small amountsof other materials. Processing continues until the desired or economicalamount of deodorization has been achieved.

In addition to the separate batch process steps of refining the priorart also includes a semi-continuous deodorization process in whichseveral functions are performed within a singular column. Heating andcooling as well as selective distillation and steam stripping areaccomplished concurrently between several trays (really tanks because oftheir size) within a common column. Present practices frequently allowthe oil product to become reaerated after degumming or caustic refiningand likewise deaeration procedures are frequently not carried tocompletion. Hence, subsequent deaeration is performed within thesemi-continuous deodorization process. The process holds all stages(large trays) for a particular "batch time" although the "batch time" isnot as long as for the batch type deodorization process. Often, lesspure oil is produced because a more pure product would require a muchlonger residence.

In both the batch and semi-continuous processes, the prior art hasattempted to decrease the absolute pressure within the column in orderto reduce the residence of the oil in the columns. Large amounts ofenergy are expended to accomplish the low pressure in order to reducethe residence and in order to make the volatile materials spring fromthe oil more quickly.

Present practice also over-heats the oil all too frequently. In thepast, the high temperatures of the column are obtained promptly byDowtherm™ heat exchangers. Exceedingly high skin temperatures of the oilare created in these heat exchangers prior to the oil entering thecolumns in order to hurry the deodorization to completion. It is wellrecognized that the longer the oil is subjected to higher temperatures,the more the oil breaks down to produce additional odoriferous materialswhich must also be removed from the oil. Of course, greater energy useto obtain higher vacuum, higher temperatures or shorter residencereduces the profitability of the process. If longer residence times arepermitted, the increase in labor and the decrease in availability of theequipment also reduces profitability.

As can be seen, the prior art methods have several disadvantages. Onesignificant disadvantage is the energy inefficiency of these processes.In order to increase the throughput of the equipment, more and morehorsepower has been utilized to increase the vacuum within the steamstripping chambers. As the current practice is not truly continuous,true product to product heat transfer cannot approach its ultimateefficiency as heat transfer is a function of time. Eductor steam has thedisadvantage of not yielding its full energy into the production of thelow pressure as all of its energy cannot be used in producing dynamicwork upon the vapors to be removed. In other words, the eductor steamcannot expend its enthalpy energy upon the system.

Another significant disadvantage of the prior art has been that themethods utilized create environmental problems due to the manner inwhich the volatile materials are discarded. For deodorization, thequantity of eductor steam plus the stripping steam may equal the mass ofthe oil being deodorized. Since all the vapors are co-mingled with thesteam flow, the total heat lost over head from the liquid oil isextravagant. Likewise, this mixture of hydrocarbon vapor and water vaporpresent a separation problem with a great deal of the hydrocarbon, whencondensed, being sent to local sanitary facilities as this effluent isnot acceptable for stream discharge. The BOD of the hydrocarbon watermixture is extremely high with most municipalities making surcharges.Desirable materials are discarded with the eductor and stripping steamwhich could be marketable if they were to remain uncontaminated. Forexample, tocopherol is frequently discarded along with fatty acids andwater.

SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to provide animproved method and apparatus for dynamically refining and deodorizingfats and oils.

Another object of the present invention is to provide an improved methodand apparatus for deodorizing fats and oils in a more efficient mannerwhich is truly continuous.

Still another object of the present invention is to provide an improveddistillation chamber and method of distillation in a chamber for use inrefining and deodorizing edible oils and fats.

Still another object of the present invention is to provide a method andapparatus for refining deodorizing edible oils and fats in an efficientmanner which concurrently fractionates the distilled vapors intodesirable by-products.

Still another object of the present invention is to provide an energyefficient and environmentally superior method for refining anddeodorizing edible fats and oils.

Yet another object is to provide an improved distillation process whichadds excitation energy for refining edible oils and fats withoutoverheating or damaging the oil.

Yet another object is to provide an improved steam distributor and steamdistributor column for use in the steam stripping of edible oils.

Yet another object is to provide an improved method for continouslycondensing low volume vapors produced in refining edible oils and fats.

In accordance with these objects, the present invention utilizes adistillation chamber having a means for driving a plurality ofrelatively thin sheets of oil having a relatively large surface areadownwardly in parallel in the chamber. A vacuum producing device isprovided at the top of the chamber, preferably a liquid ring vacuumpump. By this configuration, the vacuum is applied to a greater surfaceoil and, moreover, it is applied in a manner which more efficientlysprings the distillation vapors from the oil. The oil can be supplied tothe chamber at a temperature appropriate for distillation at thepressure of the chamber. Preferably, the chamber includes a means forheating the oil to precisely the proper distillation temperature.

A plurality of chamber nozzles to produce and properly form the drivensheets are disposed at the top of the distillation chamber. Each nozzleis preferably configured so as to drive the thin sheets of oildownwardly at a high velocity while the sheet maintains its integrityfor as far down in the column as possible. The nozzle must, therefore,produce a sheet which is uniform in thickness both horizontally andvertically. The nozzle of the present invention comprises an elongatedbody having central liquid inlet on its upper edge and an elongatedliquid outlet on its lower edge defined by first and second lips. Apressure equalization means communicates the inlet and outlet andequalizes the liquid pressure longitudinally across the outlet. Anadjustment means is provided for adjusting the shape of a sheet ofliquid driven from the nozzle.

The pressure equalization means of the nozzle preferably comprisesfirst, second, third and fourth nozzle chambers connected by first,second and third longitudinal slots, respectively. The inlet of thenozzle is connected to a central portion of the first nozzle chamber.The first slot connects the first and second nozzle chambers and tapersfrom a relatively narrow central portion to a relatively wide endportion so as to evenly longitudinally distribute the greater centralliquid pressure in the first nozzle chamber to the second nozzlechamber. The second slot connects the second and third nozzle chambersand has a plurality of uniform, evenly spaced, vertical openingsdisposed longitudinally across the slot for pressure equalization. Thethird slot connects the third and fourth nozzle chambers and has arelatively uniform width for longitudinal pressure equalization. Acentral drag plate can be provided through the chambers and slots toequalize drag on the oil sheet allowing the oil sheet to be drivenfurther prior to its breakup.

The adjustment means of the nozzle preferably comprises a plurality ofthreaded screws longitudinally spaced along the body member to exert acantilever pressure through the body member urging a portion of thefirst and second lips of the nozzle outlet to narrow or widen uponthreaded adjustment of each of said plurality of said adjustment screws.

To allow selective excitation of the to-be-vaporized components, thedistillation chamber of the present invention preferably includes amicrowave transmission device disposed for transmission of microwavesinto the oil as it enters the top of the distillation chamber. Themicrowave transmission selectively excites the volatile components topromote vaporization.

The method of distillation utilized by the present invention comprisesforming a thin sheet of oil having a relatively large surface area anddriving this sheet of oil in a distillation chamber at distillationtemperature and pressure such that a distillation vapor product isformed therefrom and such that the surface of the sheet of oil movesrapidly with respect to the distillation vapor product so as to promotefurther distillation.

Preferably, a plurality of parallel, closely spaced, thin, liquid oilsheets are formed and driven downwardly/at a relatively high velocity inthe distillation chamber. A vacuum source at the top of the distillationchamber causes the distillation vapors to move rapidly upwardly between:he sheets of oil. This method increases the speed of vaporization byincreasing the liquid surface to which an effective vacuum is supplied,by decreasing the static pressure directly adjacent to the liquidsurface, by increasing the relative velocity pressure between the vaporand liquid, and by reducing or eliminating the fluid film at the oilsurface which normally inhibits vaporization. The method likewisedecreases the distance through the liquid body through which thedistillates must travel before being liberated at the liquid surface.

Preferably the vacuum source at the top of the distillation chamber is apump which does not introduce steam into the distillation vapors. Aliquid ring pump sealed by oil or fat from the process is preferred.

In the deaeration, dehydration and distillation of all hydrocarbons, thepresent invention does not utilize stripping steam. This improvesvaporization since the steam itself inhibits vaporization by increasingthe pressure at the liquid surface and by increasing the volume ofvapors to be removed from the chamber. The present invention likewisedoes not utilize eductor steam to create vacuum in the system. Sucheductor steam puts undue mass burdens upon the vacuum effects subsequentto the primary vacuum device which vitiates the effectiveness of allvacuum systems.

The method of the present invention provides a continuous processreplacing the batch and semi-continuous processes of the prior art andproducing desirable discrete products not produced by the prior art. Inconnection with the distillation of edible oils and fats, the vaporproducts produced by the present invention can include water, air,tocopherol, fatty acids, alcohols, ketones, aldehydes and othermaterials. Such products are in a relatively pure state since thepresent invention uses no eductor steam and extracts the vapor productswithout the aid of stripping steam.

The method of the present invention is especially useful fordistillation of free fatty acids from triglycerides since it provides afast and efficient distillation which reduces the number of free fattyacids formed as a result of degradation of triglycerides duringdeodorization. The method of the present invention allows use of lowerheat exchanger skin temperatures while still providing an extremelyshort residence.

The method of the present invention provides for a series of isothermalstations for the distillation of the raw oil in stages. Each station hasa relatively constant temperature established by the leaving (finishedoil) flow exchanging its heat to the entering (unfinished oil) flow. Inthe continuous condition of operation, only trimming heat is added ateach isothermal station plus individual heat trimming at each of thedistillation chambers, as is needed, to compensate for heat losses asthe liquid moves through the distillation chambers. A sufficient numberof the distillation chambers are used in series within an isothermalstation so that distillation goes to completion, if desired.

Preferably, the method includes a completely continuous distillationprocess with separate isothermal stages for deaeration and dehydration,bleaching low temperature refining, tocopherol distillation, hightemperature refining, and steam stripping of peroxides andhydroperoxides. Except for bleaching, each such stage includes at leastone distillation chamber utilizing the driven sheet distillation methodof the present invention. Separate stages or equipment within stages canbe provided for degumming and bleaching for a totally continuous,complete refining and deodorizing system.

The method also preferably includes a unique vapor system. Vacuumdevices which do not add mass to the system, such as liquid ring vacuumpumps, are used instead of steam eductors of the prior art to providevacuum to the distillers. This maintains a low vapor pressure and moreefficient vacuum in the vapor recovery system. It also allows directcondensation of desirable products such as tocopherol, fatty acids, etc.Staging of the liquid ring pumps, use of the countervelocities in thedistillation chambers and condensation of the vapors greatly improve theefficiency of applying vacuum to the liquid for distillation.

As an example of an isothermal station of the type used with thecontinuous process of the present invention, the tocopherol distillationstation will now be described. Prior to this staall aldehydes, alcohols,etc. have been removed from the unfinished oil or fat so that the nextvolatile component, tocopherol, remains in solution in the oil and fat,but no components with a lower boiling temperature remain. As the oil orfat is moved into and heated to the temperature of the next isothermalstation, only hydrocarbons at or above the boiling temperature oftocopherol will go overhead. The overhead vapors are conveyed to arectifying column which produces virtually pure tocopherol. Thetocopherol is separated as a pure product suitable for sale as is. Theliquid ring vacuum pump above the rectifying column is sealed with theliquid phase tocopherol product as any other sealant would contaminatethe pure tocopherol produced. The production of tocopherol in thisisothermal station occurs continuously as all other processes, such asremoval of free fatty acids, also are continuously proceeding.

This process can be continuous with low residence time due to theefficiency of distillation produced by the driven sheet method ofdistillation. This driven sheet method provides a large surface areasubjected to both low pressure and to high velocity distillation vaporsmoving upwardly in the distillation chambers. Accordingly, no singlestation is a constant limiting factor in the complete refining anddeodorization.

In order to provide efficient condensation of the low volume, low flow,tocopherol the present invention circulates the distilled tocopherolvapor through a condenser having separated upper and lower sections.Vapor in the upper section is continuously recirculated over condensingcoils at a rate sufficient to produce turbulent flow for good heattransfer. Liquid condensing in the upper section moves through a liquidseal to the lower section where a level control pump can remove producttocopherol from the process.

Although all other isothermal stations of the method of the presentinvention do not use steam, a final subsection does utilize strippingsteam but not eductor steam. This final subsection is provided to removeperoxides and hydroperoxides. This steam stripping subsection issupplied with super-heated steam to eliminate thermal shock upon the oilwhich occurs by the use of saturated steam at almost any practicalpressure. This procedure eliminates the hazards of overheating the oilor fat (to compensate for the heat loss) at its highest temperature. Thesubsection includes driven-sheet distillation chambers in series similarto those previously described. However, the level of liquid in thecolumns is higher, than in the other columns to allow more contact withthe stripping steam.

Preferably, the stripping chamber has disposed at its lower end beneaththe normal liquid level a special distribution device (for distributionof super-heated steam evenly throughout the liquid in the strippingchamber) which maximizes the ratio between the surface area of the steamto its mass for the purpose of rapid reaction with the peroxides andhydroperoxides. The distribution device includes a plurality ofrelatively small tubes connected to a distribution body having adistribution chamber therein. The tubes have narrow interior passageswhich limit the flow of gas therethrough for production of optimalbubble size in the liquid. This sub-section of the final isothermalstation has its own vapor recovery system which operates independentlyof the balance of the isothermal station.

For a further understanding of the invention and for further objects,features and advantages thereof, reference may now be had to thedrawings taken in conjunction with the following description ofpreferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic view of a process of refining fats and oils inaccordance with the present invention.

FIGS. 2A-2F show a more detailed schematic view of the process of FIG.1.

FIG. 3 is a partial side view of a distillation column constructed inaccordance with the present invention.

FIG. 4 is a plan view of the column of FIG. 3 with the top removed.

FIG. 5 is a side view of a portion of a distillation column nozzleconstructed in accordance with the present invention.

FIG. 6 is a cross-sectional view of the portion of a nozzle shown inFIG. 5 taken along the lines shown in FIG. 5.

FIG. 7 is a cross-sectional view of the portion of a nozzle shown inFIG. 5 taken along the lines shown in FIG. 5.

FIG. 8 is a cross-sectional view of the portion of a nozzle shown inFIG. 5 taken along the lines shown in FIG. 5.

FIG. 9 is an end view of a nozzle constructed in accordance with thepresent invention.

FIG. 10A is a cross-sectional view of the nozzle shown in FIG. 5 takenalong the lines shown in FIG. 5.

FIG. 10B is a cross-sectional view of the nozzle shown in FIG. 5 takenalong the lines shown in FIG. 5.

FIG. 10C is a cross-sectional view of a nozzle insert piece for thenozzle shown in FIG. 10A.

FIG. 11 is a schematic side view of a nozzle arrangement in adistillation column of the type shown in FIG. 2.

FIG. 12 is a schematic side view of a steam stripping column of thepresent invention.

FIG. 13 is a cross-sectional view of a steam distributor of the steamstripping column of FIG. 12.

FIG. 14 is a cross-sectional view of a tip of a tube of the steamdistributor of FIG. 13.

FIG. 15 is a side cross-sectional view of a portion of a surfacecondenser of FIG. 2D.

FIG. 16 is an enlarged schematic view of a portion of the process shownin FIGS. 2A-2F.

FIG. 17 is an enlarged schematic view of a portion of the process shownin FIGS. 2A-2F.

DESCRIPTION OF PREFERRED EMBODIMENT

Referring now to FIG. 1 and FIGS. 2A-2F, the method and apparatus of thepresent invention are shown schematically. The present invention differsin its most dramatic respects from refining and deodorizing of edibleoils and fats of the prior art in that the entire process is continuous,steam is used only in one portion, the distillation is more efficientand produces discreet and valuable products, and the process does notproduce products which are difficult to dispose. As is apparent throughan understanding of the present invention, most of these differences aremade possible by the method and apparatus of distilling by drivensheets, disclosed below.

It is well known that evaporation and distillation are surfacedependent. Thus, the more surface a liquid presents, the moreevaporation will occur. Further, it is well known that evaporation isinfluenced by the vapor pressure and the vapor motion adjacent to theliquid surface. Thus, a lower vapor pressure produces a fasterevaporation and a faster vapor motion adjacent to the liquid surfaceproduces a faster evaporation. With respect to the vapor motion, theinfluence of vapor motion on evaporation rates increases as the vaporpressure above the liquid surface decreases. This is because one aspectof evaporation is convection of the evaporated molecules away from theliquid surface and convection proceeds faster with a faster vapor motionadjacent to the liquid surface.

It is also well known that liquids have a fluid film which acts as abarrier to vaporization (see, for example, Walker, Lewis and McAdams,Principles of Chemical Engineering, 1927, pages 40-42). The film iscreated by molecules vaporizing from the liquid surface with relativelylow velocity. These low velocity molecules insulate the liquid surface.Movement away from the fluid film requires a force applied to the filmand most distillation processes are relatively inefficient in applyingthis force.

In a fluid film produced by a liquid having multiple components, thefilm will contain both lighter, more volatile molecules and heavier,less volatile components. To move these molecules from the film adynamic force must be applied and since dynamic force equals mass timesacceleration, the force to move the heavier molecules is greater thanthe force to move the lighter molecules. Therefore, the lightercomponents will vaporize more rapidly and act as a barrier to thevaporization of the heavier components.

With respect to liquids having two or more components differing in theirvolatility still another factor becomes important to evaporation. Thisfactor is the time for migration of the more volatile componentmolecules in the liquid to the liquid surface. Accordingly, the relativethickness of a liquid with two components affects the ability of thatliquid to evaporate the more volatile component.

In a liquid such as raw vegetable oil, there are volatile componentssuch as free fatty acids and tocopherol in less volatile triglycerides.In oil and fat refining and deodorizing, these triglycerides must remainbelow their degradation and polymerization temperatures. In thissituation, it is not possible to simply heat the material to drive offthe volatile components since the amount of time to drive off thevolatile components at a temperature lower than a damage temperature istoo long. Accordingly, the pressure is lowered to increase the rate ofdistillation at safe temperatures.

The prior art methods of low pressure distillation recognize that nomatter how great the vacuum which is applied at the top of a column, itis difficult to apply that vacuum to a large surface area of material.The prior art may produce a static pressure near 0.5mm Hg at the primaryvacuum device, while at the actual surface where vaporization is takingplace, the static pressure will be on the order of 50mm Hg. This is dueto the static pressure gradient between the vaporizing surface and theprimary vacuum device caused by the presence of the vapors, both waterfrom the stripping steam as well as the hydrocarbons themselves.

Likewise, for steam stripping it is assumed that effective distillationis taking place throughout a liquid body. This is simply not true as thestatic liquid pressure below an oil surface diminishes the desiredvacuum by static liquid head of the oil above the point of distillation.Finally, the relative thickness of the liquid and migration of thevolatile components to the surface of the liquid is a significanthinderance to distillation of the volatile components. Adding more traysreduces the liquid thickness but drastically increases the column size,reduces flow rates through the column and increases pressure dropthrough the column. Prior patents such as U.S. Pat. No. 2,280,896 toDean recognize this problem.

The present invention avoids the problems of the prior art by providinga distillation chamber having a plurality of relatively narrow andelongated nozzles at the upper end thereof to drive relatively thinsheets of oil or fat downwardly in the chamber. These sheets areparallel to each other and closely spaced to improve the velocities ofthe vapor counterflow. The nozzles are precise to maintain the integrityof the sheets for as long as possible as they move downwardly in thechamber.

At the upper end of a chamber of the present invention, a vacuum sourcesuch as a liquid ring vacuum pump creates a relatively low pressure atthe top of the column. Unlike the columns of the prior art, the amountof surface area directly affected by the vacuum source is much greater.More importantly, the distilled volatile materials which leave theliquid surface as the sheets are driven downwardly move rapidly upwardlytoward the vacuum source at the top of the chamber as the diameter ofthe chamber is relatively small and the vapor sections between thedriven sheets of oil or fat are narrow. Accordingly, there is arelatively high velocity between the sheets of liquid driven downwardlyinto the chamber and the volatile vapor products moving upwardly in thechamber. This relative motion assists in improving distillation due tothe action of the vapor molecules on the liquid surface and thosemolecules adjacent the liquid surface.

Thus, the distillation of oil and fat provided by the present inventionemploys closely-spaced unsupported sheets of oil driven at high velocitythrough a vacuum chamber. The sheets of oil move downwardly at highvelocity while the volatile vapors move upwardly at relatively highvelocity. The static vapor pressure adjacent to the enlarged surfacearea is maintained relatively low due to the velocity energy, likewise,adjacent to the liquid surfaces. The dynamic sheer between the vapormass and the liquid mass encourages distillation by reducing oreliminating the insulating fluid film adjacent to the liquid surface.The relatively thin sheets of oil promote rapid vaporization of the morevolatile components due to the relatively short distance through whichvolatile molecules must migrate to the liquid surface.

The present invention also utilizes a multiplicity of vacuum chambers inseries for each of the distillations. In this way, not one but severalvacuum sources can be applied to a distillating volatile product. Thisincreases the surface area to which the vacuum source is applied andprovides flexibility for oil having greater or lesser quantities of aparticular distilled component.

The provision for a separate set of vacuum chambers for each distilledcomponent provides a significant advantage over the prior art singlechamber for all fractions since the separate fractions occursubstantially one after another whether distilled in one chamber ormany. In other words, substantially all of each of the volatilecomponents must distill prior to the next component having a significantdistillation rate. In a single column distillation of all volatiles, thedistillation of the first volatiles hinders distillation of the secondproducing an undesirably long residence necessary for a desired refiningand deodorization. The series of distillation chambers provided by thepresent invention for each component avoids this inefficiency.

Referring now to FIG. 1 and FIGS. 2A-2F, a complete refining anddeodorizing process in accordance with the present invention is shownschematically. As shown, degumming, deaerating, dehydrating, bleaching,low temperature refining, tocopherol distillation; the fatty aciddistillation, and steam stripping all occur simultaneously at fiveisothermal stations. At isothermal station 10, degumming, dehydrationand deaeration occur at approximately 160° F. At isothermal station 12bleaching occurs at approximately 230° F. At isothermal station 14refining distillation to remove ketones, aldehydes and other componentsoccurs at approximately 285° F. At isothermal station 16 tocopheroldistillation occurs approximately 290° F. as measured at the top of thetocopherol rectifying column. At isothermal station 18 fatty aciddistillation occurs at approximately 490° F. Finally at subsection 20 ofisothermal station 18, steam stripping occurs to remove peroxides andhydroperoxides at approximately 490° F.

Between each of the stations having a different temperature and at thebeginning of the process is a heat exchanger exchanging heat from thefinished oil to the unfinished oil moving into the next station. In thismanner, an efficient use of the heat applied to the oil is obtained.After startup, assuming a relatively well insulated set of equipment,relatively little heat is lost as waste heat. No significant amount ofoil or fat product heating or cooling is required throughout theprocess.

Raw oil enters the process through stream 22. It exchanges heat withinheat exchanger 24 with a stream 26 of finished oil or fat leaving thesystem. The unfinished but now heated oil in stream 22 then entersisothermal station 10 for degumming, dehydration, and deaeration. Waterand air exit the isothermal station 10 at a stream 28. The unfinishedbut now degummed, deaerated, and dehydrated oil in stream 22 then exitsisothermal station 10 and enters heat exchanger 30. At heat exchanger30, the unfinished oil in stream 22 again exchanges heat with theproduct oil 26.

The unfinished oil in stream 22, after heat exchange in heat exchanger30 then enters the isothermal station 12 for bleaching. Except forincluding bleaching and heat exchange as part of the continuous processof the present invention, the bleaching process used in isothermalstation 12 is well known in the prior art.

Following bleaching the unfinished oil in stream 22 is conveyed to heatexchanger 32 where the unfinished oil again exchanges heat with thefinished oil in stream 26. This further heated unfinished oil thenenters isothermal station 14 for a relatively low temperaturedistillation for removing aldehydes, ketones, alcohols, and thosecomponents toiling at a temperature less than the temperature of removalof tocopherol. In other words, the separation in isothermal station 14removes all components which are more volatile than tocopherol. Theremoved components exit in stream 34 and the unfinished oil, followingthe removal of these components continues in stream 22 to heat exchanger36.

In heat exchanger 36 the unfinished oil again exchanges heat withfinished oil raising its temperature for distillation of tocopherol inthe isothermal station 16. The isothermal distillation in station 16produces an essentially pure stream of tocopherol 38. This puretocopherol is a very valuable product of the present invention and thisproduct is not achieved in this manner by any of the prior art.Following removal of the tocopherol the unfinished oil from station 16enters a heat exchanger 40.

Following a final heat exchange between unfinished oil and finished oilin heat exchanger 40, the unfinished oil enters an isothermal station 18for distillation of free fatty acids. The free fatty acids exit theisothermal station 18 in stream 42. Preferably, the free fatty acids arethen fractionated and condensed into the several free fatty acidsfractions.

The unfinished oil from station 18 then enters the final subsection 20of isothermal station 18. The subsection 20 is a part of isothermalstation 18 although it performs the stripping function while the balanceof isothermal station 18 does not. It is necessary to keep separate thesteam vapor products found in the subsection 20 from the balance ofisothermal station 18 so that free fatty acid products may be discretelyrecovered.

In subsection 20 of isothermal station 18, the unfinished oil is steamstripped to remove peroxides and hydroperoxides from the triglycerides.The water, peroxide and hydroperoxide vapors leave the subsection 20 bysteam 44 and the finished oil leaves subsection 20 in stream 26.

Referring to FIGS. 2A through 2F as well as FIGS. 16 and 17, an examplecontinuous edible oil distillation process of the present invention isshown schematically in more detail. Heat exchangers 24, 30, 32, 36 and40 are redundantly shown on appropriate pages of the drawings to aid inunderstanding the flow connections. Distillation chambers 51-56, 61-64,71-74, 81-88 and 91-94 are all vacuum distillation chambers utilizingdriven sheets as described above. The chamber top and the nozzleconstruction and arrangement are shown in greater detail in FIGS. 3through 11. The steam stripping column components which relate to theaddition of steam are shown in greater detail in FIGS. 12 through 14.

Unfinished oil continuously enters the system through stream 102 drivenby metering pump 104. An example of unfinished oil would be finelyscreened soybean oil. This unfinished oil would have about 0.4% freefatty acids and 0.1% tocopherol with the balance being essentiallytriglycerides. Other components such as phosphatides, chlorophyll, anddissolved oxygen are also present in small quantities. As the unfinishedoil enters at stream 102 it typically has a temperature of approximately70° F.

The unfinished oil in stream 102 enters a heat exchanger 24 where theunfinished oil exchanges heat with finished oil which enters the heatexchanger in stream 106 and exits the heat exchanger at stream 108. Thefinished oil in stream 106 typically has a temperature of 170° F. andstream 108 typically has a temperature of 80° F.

The unfinished oil which exits exchanger 24 exits in a vapor stream 110and a liquid stream 112. The vapor stream 110 and the liquid stream 112are both approximately 160° F. The liquid stream passes through acontactor 114 which allows additional vapor from the unfinished oil toenter stream 110. A liquid stream 116 exits the contactor 114. Theliquid stream of unfinished oil which has been heated to approximately160° F. enters a heat exchanger 118 which provides trim heat or start upheat to the oil prior to entering blender 122. Saturated steam isprovided to heat exchanger 118 by means of stream 120.

Following heat exchange in heat exchanger 118, stream 116 of unfinishedoil passes through a blender 122, a high speed mixer 124, and acentrifuge 126 for the addition and removal of phosphoric acid andwater. This removes phosphatides and some water from the unfinished oilstream 116. This is the first stage of degumming.

The stream 116 is pumped by a pump 128 through a trim heater 130 priorto entering the top of vacuum distillation chamber 51. The trim heater130 supplies small amounts of heat to the unfinished oil with steam orelectrical energy or heat from a side stream of finished oil. After trimheating the stream 116 enters a microwave exciter 132 at the top ofchamber 51. The microwave exciter 132 selectively excites the water andmore volatile components of the unfinished oil compared to thetriglycerides and less volatile components. Little heat is transferredinto the unfinished oil by the microwave exciter as the exposure of theoil to it is extremely short. Nevertheless, the selective excitation ofthe more volatile components promotes distillation without harming theoil. The configuration of the microwave exciter with respect to thenozzles in the upper portion of the vacuum distillers is described inmore detail below.

The pump 128 supplies constant pressure (this constant pressure isadjustable to allow proper sheet configuration of the oil) to the oil orfat in the nozzles in the top of chamber 51. This importantly allowseach nozzle to produce a uniform, thin sheet of oil. A constant pressurevalve 134 is provided in stream 116.

Providing vacuum to vacuum distillation chamber 51 is a liquid ringvacuum pump 136. The suction side of the pump is connected to the top ofvacuum distillation chamber 51. The discharge of the pump 136 is intothe vapor stream 110 which exits the heat exchanger 24.

At the bottom of chamber 51 is a level control 138. The effluent 142 atthe bottom of chamber 51 has the static vapor pressure of the chamberitself plus the liquid head pressure of the height to the liquidsurface. Hence, pump 144 is a magnetically driven pump with no shaftseals through which atmospheric air may leak into pump. Pump 144pressures the unfinished oil to 35 to 50 pounds per square inch. Thus,mechanical seals are permissible for the higher pressure pumps (such aspump 128 and 143 and equivalent pumps on the remaining distillationchambers).

Likewise all valves in the liquid flow will have a pressure greater thanatmospheric and, hence, will not allow air to contaminate the liquidspassing therethrough. An orifice plate 145 is placed in stream 146upstream from the check valve 148. Its purpose is to flow preferentiallylarger portions of the unfinished oil in the direction of the valve 140,thus requiring pump 128 to receive nearly all of its suction flow fromthe unnumbered flow 116 from the centrifuge 126. This arrangementtogether with the other flow controls and valves is capable ofdischarging the exact flow it receives from any component. When theentire apparatus is operating at full capacity, little flow passesthrough stream 146 or similar streams. In other words, this arrangementprovides flow control through all components established by meteringpump 104.

As is apparent from the drawings, each of the distillation chambers51-56, 61-64, 71-74, 81-88 and 91-94 has similar apparatus for flowingoil in driven sheets, heating, level control, suction and reflux.Therefore, the apparatus descriptions for each of the remaining chamberswill not be described since it is the same as that described forchambers 51 and 52.

The outlet stream 142 of unfinished oil from distillation chamber 51enters a second distillation chamber 52 which is in series withdistillation chamber 51. Together these distillation chambers provide afirst dehydration and deaeration of the unfinished oil. A major portionof the water and dissolved oxygen are removed from the oil in chambers51 and 52.

A liquid ring vacuum pump 150 provides vacuum to chamber 52. The liquidand vapor effluents from both vacuum pumps 136 and 150 is to the vaporstream 110. The stream consists of water vapor, air, unfinished oil usedfor liquid ring pump sealant and unfinished oil entrainment. In fact, asmall amount of entrained oil is needed if the system is to operate atits highest efficiency. The driven sheets of oil must be driven at veryhigh velocities in order to obtain the maximum benefit of the vaporizingefficiencies unique this process. Such high velocities cause parts ofthe driven sheets of oil or fat to shear creating small particles to beentrained in the rising vapors.

Following dehydration and deaeration in chambers 51 and 52, theunfinished oil enters a blender 152, a high speed mixer 154, and acentrifuge 156 where malic acid and some water are added and removed.This further removes phosphatides from the unfinished oil. This secondstage of degumming is more efficiently accomplished with the removal ofwater which was achieved in chambers 51 and 52.

Following the second stage degumming, unfinished oil then is conveyedthrough distillation chambers 52 through 56 in series for furtherdeaeration and drying. The oil at this stage should be completelydeaerated because of its vulnerability to autooxidation followingdegumming. Liquid ring pumps 158, 160, 162, and 164 supply vacuum toeach of the distillation chambers 53, 54, 55 and 56 respectively, andexhaust water, oxygen, liquid ring pump sealant and entrained oil or fatto stream 110.

Referring especially to FIG. 17, the overhead vapors stream 110 whichgathers the distilled vapors from chambers 51-56 enters the suction sideof a liquid ring vacuum pump 166 which provides an improved effectivevacuum to the chambers 51-56. The pump 166 drives a liquid and vaporstream 177 to a bubble-cap column 168. A vertical stream 196 which is acontinuation of streams 110 and 194 carries the liquid phase materialswhich may condense or which are carried as entrainment in streams 110and 194 to bubble-cap column 168. These liquids consist of any condensedvapors, unfinished oil entrainment having come out of entrainment andthe liquid ring pump sealant of unfinished oil. The conduit throughwhich stream 110 flows should be sloped to allow liquid which flowstherein to move rapidly to vertical stream 196, preventing liquid fromfilling the conduit and from entering pump 166. Liquid from stream 196must enter the column below a point where the pressure in stream 110 andthe discharge pressure from vacuum pump 166 are balanced with the liquidhead of the unfinished oil.

The bubble-cap column 168 separates less volatiles and the entrained oil(as much as 0.5% of the product flow is desirable) which enter stream110 and a portion of this oil is supplied through stream 170 as asealant to the liquid ring pumps 136, 150, 158, 160, 162, 164, and 166.The sealant oil to these pumps is moved by a pump 157 and is cooled by acooler 169 fed by cooling water in stream 171.

Flow of sealant oil to the pumps 136, 150, 158, 160, 162, 164 and 166 islimited by constant flow valves 137, 151, 159, 161, 163, 165 and 167adjacent each pump. This maintains the proper amount of sealant to eachpump.

A recirculation stream 172 is provided on bubble-cap column 168. A trimheater 174 and a pump 176 are provided for heat and circulation of thisstream 172. This recirculation prevents water from exiting the bottom ofcolumn 168.

Vacuum is applied to the top of bubble cap column 168 by a liquid ringvacuum pump 180. Water and oxygen which exit overhead of the bubble-capcolumn 168 are conveyed to a phase separator 178 through vacuum pump180. The vacuum pump 180 is sealed with water through stream 183condensed in the bottom section of the phase separator 178. The sealantwater 183 is pumped to the vacuum pump 180 by pump 179 through heatexchanger 181 cooling the stream 183. Cooling water flow 171 is providedto exchanger 181 for the cooling.

Entrained oil which is not utilized as sealant to the pumps is conveyedto the stream of unfinished oil 102 entering station 10, by means ofstream 184. A level control 186 is provided at the bottom of bubble-capcolumn 168 and a valve 188 on stream 170 opens and closes responsive tothe level control 186. Pump 157 motivates the flow. Stream 184 is drivenby a product transfer pump 185 along with four valves 187, 189, 191 and193 which allow the pump 185 to flow the unfinished oil or fat in thedirection of the incoming stream 102 or the next station 12. Thisarrangement is used in start-up for establishing the initial temperatureof the respective isothermal stations by flowing to the left. Thearrangement of the pump 185 and valves 187, 189, 191 and 193 on conduit184 and conduits similar to conduit 184 in other isothermal stationsalso have the purpose of evacuating the isothermal station when flowingto the next station. By stopping flow through metering pump 104 andrefluxing the contained oil or fat within the isothermal station byflowing stream 184 to stream 102, the oil in each station may be refinedto the degree to which that respective station is capable. Once theentire containment of the isothermal station is thusly refined ordeodorized, flow to the next station evacuating the present station isaccomplished by the various transfer pumps such as pump 144 and pump 185on stream 184. Hence, the disclosed apparatus and system are capable ofrefining and deodorizing to completion all of the oil or fat containedin each individual station as well as continuously through all stations.

Likewise, it is unnecessary to evacuate the entire five isothermalstations to change an oil or fat product. By evacuating one station andallowing its chambers and piping to drain, the containment therefrom isevacuated forward into subsequent processing of the first oil or fat.While the evacuation process proceeds, partial reflux takes placethrough streams such as stream 184. The second oil or fat is introducedinto the now evacuated isothermal station. With this sequence, thesecond oil or fat is continued throughout the entire apparatus while itstill enjoys most of the heat transferred from the leaving first oil orfat.

Referring still to FIGS. 2A-2F, the unfinished oil which has beendeaerated and dehydrated in chambers 51-56 enters heat exchanger 30.Heat exchanger 30 exchanges heat from a finished oil stream 190 enteringthe heat exchanger 30 at approximately 230° F. Any vapors released bythe increase in temperature from the oil or fat are carried in stream194 which is provided at the top of exchanger 30 allowing the vapors toexit exchanger 30. Stream 194 flows vapors to stream 110 and both areconnected to vertical stream 196.

Stream 192, at approximately 230° F., enters a mixer 200 where dried anddeaerated clay are mixed with the oil for bleaching. A heat exchanger202 on stream 192 is provided for trim heating. Stream 192 then enters afirst set of pressure filters 204 which are provided in parallel on thisstream to remove the clay, chlorophyll, and color chemicals from thestream. A level controlled tank 206 is disposed on stream 192 prior tofilters 204 and is connected to a valve 208 downstream of filters 204 tomaintain the flow through filters 204 at the rate oil is supplied tofilters 204. The unfinished oil from filters 204 then enters a secondlevel control tank 210 and a second set of pressure filters 212 disposedin parallel. The second set of filters are polishing filters whichfurther remove the clay and color chemicals. The pressure filters andthe devices for adding deaerated clay are well known in the bleachingart. Recycle, if necessary or desired in the bleaching isothermalstation can be provided in stream 216.

Unfinished oil in stream 214 from the second set of filters 212 enters aheat exchanger 32 for again exchanging heat with finished oil.Unfinished oil enters heat exchanger 32 in a stream 214 at approximately230° F. and exits heat exchanger 32 in stream 302 at approximately 285°F. The finished oil enters heat exchanger 32 via stream 304 atapproximately 295° F. and exits via stream 190 at approximately 240° F.Vapor from the unfinished oil stream which enters heat exchanger 32 canexit the heat exchanger in a stream 306. Liquid in stream 302 enters acontactor 308 to further allow vaporization and the vapor from thiscontactor enters stream 306.

The stream of unfinished liquid oil 302 is conveyed through distillationchambers 61-64 connected in :he same manner as distillation chambers53-56. At this isothermal station, distillation chambers 61-64 removeall components more volatile than tocopherol. These components areessentially alcohols, aldehydes and ketones. Liquid ring pumps 310, 312,314 and 316 provide suction to the top of chambers 61-64. Entrained oil,sealant oil and vapors are conveyed to bubble cap column 318 by liquidring pump 320 for separating and recycling the entrained oil andsupplying unfinished oil for sealant to the liquid ring pumps. Liquidring pump 324 conveys overhead vapors of aldehydes, alcohols, etc. to aphase separator 322. The liquid ring pump 324 uses a special sealantsuitable for high temperature which is collected at bottom of phaseseparator 322 and pumped by pump 323 through exchanger 325 where it iscooled by cooling water 171.

The underflow unfinished oil from the distillation chambers 61-64 isconveyed via stream 326 to heat exchanger 36. This again provides heatexchange between the unfinished oil and finished oil. The unfinished oilenters at approximately 285° F. and exits in stream 402 at approximately300° F. or a temperature which will produce a 290° F. temperature at thetop of rectifying column 412. Tocopherol will vaporize at thistemperature.

Following heat exchange in heat exchanger 36, the unfinished oil isconveyed to distillation chambers 71-74 for removal of tocopherol. Thedistillation chambers 71-74 are of the same type and have the sameapparatus configurations as the distillation chambers 53-56 and 61-64.Liquid ring pumps 404, 406, 408 and 410 are connected on their suctionside to each respective distillation chamber. The liquid ring pumps aresealed with entrained oil separated in a rectifying column 412 from theoverhead from distillation chambers 71-74. A rectifying column 412 withmany trays is used in order to separate relatively pure tocopherol fromfree fatty acids. The lower four trays of the rectifying column are usedfor entrained oil separation.

A reflux circulator and heater 414 is provided on the side of rectifier412 to heat the oil for rectifying and to continuously recirculate oilfrom the bottom of the rectifying column 414 to the fifth tray of thecolumn. This ensures that all rising vapors entering the rectifyingcolumn encounter downwardly flowing heated oil.

A second reflux circulator and heater 416 extends between the sixth andeighth trays of the rectifying column 412 again heating andrecirculating free fatty acids from a lower portion of the rectifyingcolumn 412 to a higher portion. A product recovery tank 418, is attachedto the sixty tray to recover lower boiling temperature free fatty acidswhich will rise in the rectifying column to this tray. A vaporconnection 420 extends from the product recovery tank 418 to therectifying column 412 to equalize pressure in the 448 as liquid entersand leaves the tank responsive to a level control in the tank.

A level control 422 is disposed in the bottom of rectifier 412 tocontrol the level of oil which is retained in the rectifier 412. A pump424 pumps the excess oil back to stream 322, entering heat exchanger 36by way of stream 426. The flow through stream 426 is controlled by avalve 428, responsive to the level control 422.

Pump 424 also pumps oil to liquid ring pumps 404, 406, 408, 410 and 411as sealant. The sealant oil is cooled prior to entering the pump by acooler 430. Constant flow valves just prior to each pump control theflow of sealant to the pumps.

A liquid ring pump 432 provides suction to the top of rectifier 412 andis sealed by tocopherol product from a surface condenser 434. By usingpure tocopherol as sealant to the pump 432 the overhead vapors from therectifier 412 are not contaminated. The outlet of the liquid ring pump432 supplies essentially pure tocopherol to the surface condenser 182.

The tocopherol vapors from rectifier 412 are conveyed to surfacecondenser 434 through stream 438. The tocopherol stream 438 enters thetop of surface condenser 434 and moves over the coils of the surfacecondenser fed by the cooling water stream 171. The flow of tocopherol instream 438 is very slow and yet it is desirable to have turbulent flowof vapors over the coils to improve heat transfer. Accordingly,magnetically driven vapor recirculation blowers 440 recycle vapors fromthe bottom of condenser 434 to the top of condenser 434 at a ratesufficient to provide turbulent vapor flow over the coils. The blowersare magnetically driven to prevent any air contamination of thetocopherol due to failing blower seals.

Referring also to FIG. 15, it can be seen that the bottom of the surfacecondenser 434 is divided into two areas or chambers 442 and 444 by aplate 446 which slightly slopes to the center across the bottom ofcondenser 434. The two chambers plus the adjustable cup liquid sealbetween them, provide a controlled pressure differential favoring theupper chamber with higher pressure to aid the vapor reflux flow by theblowers. The very small amounts of tocopherol vapor conveyed to andexiting from pump 436 form a vapor stream 437, are mixed with vaporsunable to be condensed in the next isothermal station and are gatheredin a tank 439. Liquid from tank 439 is pumped through a chiller 441 andreturned as sealant to pump 436 by a stream 443.

A pipe 448 extends down from the center of plate 446 into a cup 450which is filled with tocopherol liquid condensed from the upper chamber442. As more tocopherol condenses the liquid overflows the cup and fallsinto lower chamber. The liquid in cup 450 extends about the lower end ofpipe 448 to seal the upper chamber 442 from the lower chamber 444. Thepressure differential between chamber 442 and chamber 444 is the liquidheight in the cylinder 448.

The cup 450 is supported by a threaded central rod 452 which is fixed tospiders 454 and 456 in cylinder 448. By threaded movement of the cup 450on the rod 452 the height of liquid in cylinder 448 can be adjustedwhich, in turn, adjusts the pressure differential between chambers 442and 444.

Liquid tocopherol gathers in the lower chamber 444 of the condenser 434and the level of this liquid is controlled by a level control 458. Apump 460 is provided to draw the tocopherol from this liquid incondenser 434 by way of stream 462. A valve 464, responsive to the levelcontrol 460, controls flow in stream 462. Pump 460 also suppliestocopherol sealant to liquid ring pump 432 through stream 466.

As can be seen, six different effects of vacuum energy are applied toprovide a vaporization of and separation of tocopherol from unfinishedoil. The first effect is the counter velocities between the liquidsurfaces of the driven sheets of oil or fat and the vapor velocitiesleaving overhead each distillation chamber. The second effect is theliquid ring pumps 406 through 410. The third effect is the liquid ringpump 411 connected to the outlet of pumps 406 through 410. The fourtheffect is the liquid ring pump 432 providing suction to the rectifier412. The fifth effect is the surface condenser 434 which providessuction due to condensation of the tocopherol vapors. And, finally, thesixth effect is the liquid ring vacuum pump 436 which provides suctionto the surface condenser 434. By means of the staged vacuum sources, anincreased efficiency for each is achieved.

Referring now to FIG. 2E, the unfinished oil from the tocopheroldistillation chambers 71 through 74 enters heat exchanger 40 via stream468 at approximately 300° F. and exits via stream 502 at approximately480° F. Finished oil at approximately 490° enters the heat exchanger 40via stream 504 and exits via stream 470 at approximately 310° F.

As with the previously described isothermal stations, the fatty aciddistillation station flows the unfinished oil through distillationchambers producing a vapor (mainly free fatty acids but also includingsome entrained triglycerides) and a liquid unfinished oil. This stationalso includes a similar six effect vacuum system for supplying thevacuum for distillation. The configuration of the pumps, distillers, andsurface condenser are essentially the same as described in theseparation system for tocopherol. In place of the rectifier 412 is afractionator 510. This allows separation of free fatty acids havingdifferent boiling temperatures and provides for discrete productseparation and removal. Separate free fatty acids taken from varioustrays of fractionator 510 exit in stream 512, 514, 516 and 518 as wellas from the bottom of the surface condenser.

The unfinished oil from the distillation chambers 81 through 88 isconveyed at approximately 490° as underflow from the distillationchambers in stream 520. Citric or malic acid is added to the stream 520by a mixer 522 to separate the peroxides and hydroperoxides at thedouble carbon bonds of the unsaturated oils or fats.

The underflow unfinished oil in stream 520 is then conveyed to thestripping steam station for removal of peroxides.

The distillation-stripping chambers 91 through 94 receive the unfinishedoil from stream 520 in series and are essentially the same as the otherdistillation chambers described above except for the addition of astripping steam distributor located at the bottom of the chambers.Stripping steam enters each distillation-stripping chamber atapproximately 500° F. through a capillary distributor described in moredetail below. The level of liquid in the distillation-stripping chamberis maintained higher in the chamber to allow the necessary percolationof steam through the oil in the chamber. The tops of the chambers stillinclude nozzles for driving sheets of the unfinished oil as necessaryfor efficient distillation.

Liquid ring vacuum pumps provide vacuum to each of thedistillation-stripping chambers 91 through 94. The pressure side ofthese pumps is connected to the suction of a liquid ring pump 602 whichconveys the overhead flow from the distillation-stripping chambers 91through 94 to a bubble-cap column 604 for removal of entrained oil. Theentrained oil recovered in the fatty acid distillation station areconveyed back to stream 468 by stream 606. A liquid ring pump 608provides vacuum to the bubble-cap column 604.

Peroxides and hydroperoxides and stripping steam are conveyed throughvacuum pump 608 and into phase separator 610. The peroxides,hydroperoxides and the stripping steam are vented to the atmospherethrough stream 44. A special high temperature sealant is returned to theliquid ring pump 608 by pump 611 after being cooled in exchanger 613.

Super-heated stripping steam is provided to the distillation-strippingchambers 91 through 94 by a boiler 620 and a superheater 622. Boiler 620supples saturated steam for the super-heater 622 as well as to variousstart-up and temperature trimming heat exchangers in various isothermalstations in the process. Super-heater 622 supplies high temperaturesuperheated steam for/steam stripping and start-up and temperaturetrimming heat for the fatty acids isothermal station. Boiler 620receives the non-condensibles from the low temperature refining,tocopherol and the fatty acid isothermal stations for complete oxidationby combustion in the furnace section of boiler 620.

Referring now to FIGS. 3, 4 and 11, the top of a distillation chamber700 (such as 51-56, 61-64, 71-74, 81-88 or 91-94) is shown. A typicaldistillation chamber 700 would have a height of approximately 3 metersand a diameter of approximately 0.7 meters. An incoming stream of oilenters the top of the distillation chamber 700 through a riser conduit702. The riser conduit 702 is connected to a pair of horizontal conduits704 and 706 which split the stream for entering on opposite sides of thedistillation chamber 700. As the oil stream enters the opposite sides ofthe distillation chamber 700, it enters a manifold 708 which spans thediameter of distillation chamber 700 from the conduit 704 to the conduit706. Extending downwardly from manifold 708 is a plurality of supplytubes 712 which enter each of the top central portions of each of thenozzles 712.

The nozzles 712 are disposed parallel to each other and are all normalto the manifold 708. Each nozzle is staggered in its height with respectto its adjacent nozzle so as, to allow closer packing of the nozzles aswell as to allow unrestricted flow of the vapors to the primary liquidring vacuum pump. Of course, the sheets of oil 714 driven by the nozzlemust not contact the adjacent nozzles. The ends of each nozzle 712 areheld by a clamp or ring 716. In this manner, the nozzles are held fixedfor uniform and constant driving of the oil sheets 714. A typical speedfor a sheet of oil from each nozzle would be approximately from 1 to 50meters/sec.

A liquid ring vacuum pump 718 is connected to a conduit which isdisposed in the upper center of a cap 722 of distillation chamber 700.As the vacuum pump 718 provides vacuum to the distillation chamber 700,the source of vacuum is, therefore, directly above the nozzles 712 whichdrive the sheets of oil 714 downwardly in the distillation chamber 700.A typical vacuum pressure at the vacuum pump 718 may be as high as 25mmHz.

A pair of microwave exiciters 724 are attached to conduits 704 and 706adjacent to the entrances to distillation chamber 700. These microwaveexciters face each other through manifold 708. Conduits 704 and 706 opento the microwave exciters 724 through plates 730 which are transparentto microwaves but, of course, prevent the oil from entering themicrowave devices 724.

Referring to FIGS. 5 through 10, a nozzle 800 (such as 712 in FIGS. 4and 11) is shown in more detail. Each of the nozzles 800 has a pair ofmated halves 802 and 804. Nozzle halves 802 and 804 are joined at theirupper midportion by threaded bolts 806 and on their ends by threadedbolts 808. A spacer 810 separates the two halves 802 and 804 and, inpart, determines the thickness of a sheet of oil extruded from thenozzle 800.

Each of the nozzle halves 802 and 804 has a central tube 812 and 814,respectively, extending from a central cavity through the midportion ofthe top of the nozzle half. The tubes 812 and 814 are joined to a singletube 816 which, in turn, joins the manifold in the top of the column(such as manifold 708 in FIG. 4). Thus, liquids moving from the manifoldto the tube 816, the tubes 812 and 814 and finally, an opening orchamber 820 at the center of nozzle 800. From chamber 820, the liquidmust pass through additional chambers 822, 824, and 826 before exitingthe nozzle 800 at the opening slit 828. Each of the chambers 820, 822,824 and 826 are defined by mated grooves on the adjoining surfaces ofnozzle halves 802 and 804.

Each of the chambers 820 through 824 is connected to its adjacentchamber so as to promote uniform pressure and distribution of liquidflow longitudinally in the nozzle. First, the chamber 820 is connectedto chamber 822 by an inclined opening 830. By inclined is meant that theopening is wider at the edges of the nozzle halves 802 and 804 than atthe midportion of these halves with a constant taper therebetween. Thishelps to equalize the distribution of pressure and flow after the liquidenters the midportion of the nozzle 800 through tubes 814 and 816.

Chamber 822 is connected to chamber 824 by a slotted opening 832. Aplurality of grooves or slots 834 extend vertically in the nozzle alongthe opening 832 to further equalize the pressure and flow of liquidlongitudinally across the nozzle 800.

Chamber 824 is connected to chamber 826 by a uniform flat opening 836.This uniform opening evens the pressure differentials created by theslots 834.

The opening slit 828 allows liquid from chamber 826 to exit the nozzle800. The width of this opening slit 828 can be precisely controlled byadjustment screws 840 provided at uniform distances across the upperedge of the nozzle 800,. These adjustment screws 840 act to press apartthe upper surfaces of the halves 802 and 804 narrowing the opening of828 as the halves are moved apart. The pressure of the liquid as itmoves through opening 828 acts to resiliently increase the size ofopening 828 and act against screws 840. A constant pressure valve 842controls the pressure of the oil supplied to each group of nozzles so asto maintain uniform pressure and, therefore, a relatively narrow,elongated uniform, oil sheet. The screws 840 are spaced longitudinallyalong the top of nozzle 800 to provide discrete longitudinal adjustmentalong the opening 828. The distance between each of the screws 840 canbe changed to allow coarse or fine longitudinal adjustment.

In some instances, it is desirable to have a drag plate 846 (See FIG.10C - plate 846 is not shown in FIG. 10A for clarity as to its design)to aid in maintaining integrity of the driven sheet from the nozzle 800.The purpose cf the drag plate 846 is to exert a central, inner liquiddrag force on liquid passing from the nozzle 800 reducing velocities atthe central portion of the liquid sheet. This balances those forces onthe surface of the liquid sheet which would tend to prematurely disruptthe sheet. The inner drag force balances the external drag force and theoil sheet driven from the nozzle maintains its integrity for a furtherdistance from the nozzle.

The drag plate 846 has an elongated uniform cross section and a flatplate portion 850 extends from chamber 822 through chamber 826. Liquidpasses evenly on each side of the plate as a result of liquid pressure.A triangular head portion 849 of drag plate 846 resides within chamber822 and rests upon the inclined upper shoulders at slotted opening 832.This retains the drag plate 846 in place. The tip 852 of drag plate 846extends to or beyond the nozzle lips at opening 828.

In preparing a nozzle for use in a column the nozzle is first fittedwith a spacer 810 which partially determines the thickness of the sheetof oil which will be formed by the nozzle. Next, the nozzle is placed ona test bench for flowing of oil through the nozzle and fine tuning ofthe driven sheets produced by the nozzle. Adjustment of the oil pressure(by valve 842) and the screws 840 optimizes the thickness durability anduniformity of the driven sheet. This is crucial to allow the sheet toremain intact for sufficient depth in the column while being driven athigh speeds. The nozzles are fitted one by one into the column and finetuned in place.

Preferably, the nozzle halves 802 and 804 are formed of stainless steelwhich has been subjected to milling for the chambers and the inclinationof opening 830 and the slots 834. However, for low temperature chambersand for a less expensive nozzle, the nozzle halves can be made ofextruded aluminum and subjected to less milling. The nozzle lips atopening 828 can be covered with a nonwetting surface 844 oftetraflouroethylene or the like to further improve the quality of thedriven sheet.

Referring now to FIGS. 12 through 14, a distillationstripping chamber900 is shown. Of special importance to distillation-stripping chamber900 is the method and device for distributing steam beneath the liquidsurface 902. A sparging nozzle assembly 904 disposed in the bottom ofcolumn 900 is shown in more detail in FIG. 13 and a tube portion of thenozzle assembly 904 is shown in more detail in FIG. 14.

The sparging nozzle assembly 904 includes a hemispherical chamber body906 closed at its lower end by a plate 908. A threaded opening 910 isprovided in the canter of plate 908 to allow super-heated steam to enterthe chamber 912 formed by the hemispherical body 906 and plate 908through an attached pipe 914.

Extending through the hemispherical body 906 is a plurality of smalltubes 916. Steam which enters the chamber 912 passes through the tubes916 prior to entering the liquid in distillation-stripping chamber 900.The size of the holes in tubes 916 determines the size of bubbles formedin the liquid as steam moves into the liquid through the tubes.

Preferably, the size of the hole 918 in tubes 916 is of capillary sizeso that as fluid flows through the tubes the flow rate is mainlydetermined by the size of the hole 918 and the length of the tube 916.In other words, fluid or gas can not flow significantly faster than anoptimum, rate because of the restriction of the tube size. A typicalhole 918 would have a diameter of approximately 0.025 to 0.25millimeters. This flow rate uniformity produces a uniform bubble sizewhich allows the optimum surface area to mass ratio of the super-heatedsteam bubbles. Also, the capillary hole size 918 and the length of tube916 prevent bubble explosion in the liquid since the superheated steamenters the liquid near the static pressure of the liquid. This isimportant since bubble explosion makes a small bubble size impossible.

The tips 920 of the tubes 916 are tapered and sharpened to a cone toreduce contact of the formed bubbles with the tips 916. This preventserratic bubble growth which can occur when there is a large metalsurface at the location of bubble initiation. Again, this creates asmall and uniform bubble size.

Super-heated steam is conveyed to the chamber body assembly 904 by apipe 914 threaded to the opening 916. The pipe 914 and its connectedchamber body assembly 904 are cantilevered in the lower end ofdistillation-stripping chamber 900. A vibrator 922 is mounted on thepipe 914 to constantly vibrate the chamber body assembly 904 and thetubes 916. Preferably, the vibrator 922 vibrates the tubes 916 up to 60kilohertz so as to decrease the bubble size produced by the tubes 916and to make the bubble size small and uniform among the tubes.

The flow through an individual capillary tube is determined by threefunctions provided there is sufficient static pressure on the fluid toexceed the velocity friction losses. They are the capillary size, thetube length and the fluid viscoscity. These determinates will provide anupper limit to the individual tube flow regardless of how much pressureis applied to the fluid as long as it is above the velocity frictionlosses. Hence, when the design of a singular tube has been made and thefluid is selected (including temperature), its flow is also determined.The total or composite flow through as assembly such as sparging nozzleassembly 904, is the individual tube flow times the number of tubes inthe assembly. Once an assembly flow is determined, the uniformity of thecomposite flow may be monitored with an extremely accurate flowmeasurement (even slight differential pressure changes across an orificeplate placed in the total flow) to determine if tube clogging or tubewash-out has occurred. With such an arrangement, the present inventionsafeguards itself from malfunctions.

Preferably a warning device 932 is provided on conduit 926 to indicateplugging of the tubes 916 or washout of the tubes 916.

The tubes 916 can be constructed of stainless steel and may be clad witha brazing material if desired.

The devices and methods described above have, been described for thecontinuous refining and deodorizing as would be typical for salad oil.If desired, continuous hydrogenation could be added to this system forother oils. Continuous processes for the hydrogenation of edible fatsand oils are part of the present state of the art and these processesare completely compatible with the present invention. The inclusion ofhydrogenizing processes would be placed up-stream of the finalisothermal station. Continuous hydrogenation processes and equipment areshown in U.S. Pat. Nos. 2,520,422; 2,520,423; 2,520,424; 3,792,067; and3,634,471.

In the system described above, blended oil and fats are mixed in theunfinished stage in their proper ratios and are fully processed in thecombined state. This is a departure with most of the present practiceswhich process the oils and then blend.

One aspect of the present state of the art not compatible with thepresent invention is heat bleaching. This process calls for a longresidence at a high temperature which is contrary to the presentinvention's objectives. As degradation of the refined and deodorized oilor fat is a function of time as well as high temperature, the presentdisclosure provides new control with extremely short retention timeduring the final isothermal station which produces a superior purity ofoil and fat while, at the same time, eliminates degradation associatedwith all other processes.

The present industry practice is to produce the lowest absolute pressureat all costs which, unfortunately, ignores the dynamics of the vaporflow in relation with the fluid film establishment. Measurements of afew millimeters of mercury vacuum are possible at the primary vacuumdevice (not at one millimeter above a distilling surface of oil or fat)with the present state of the art.

However, this has little to do with the rate of distillation since thevacuum at the liquid surfaces where distillation occurs is much higher.The present invention does not attempt to produce a vacuum (measuredstatically) near this level as it finds that such is unnecessary.

As can be seen by the above description, the methods and apparatus ofthe present invention are well adapted to achieve the objects andadvantages mentioned as well as those inherent therein. While presentlypreferred embodiments of present invention have been described for thepurpose of this disclosure, numerous changes in the construction andarrangement parts and the method can be made by those skilled in theart, which changes are encompassed within the spirit of this inventionis defined by the appended claims.

What is claimed is:
 1. A method of distilling a distillation productfrom oil comprising the steps of:downwardly driving at fromapproximately 1 to 50 meters per second sheets of oil having arelatively narrow thickness and a relatively large surface in adistillation column at distillation temperature and pressure such that adistillation vapor product is formed therefrom; forming a low pressureat the top of said distillation column above said sheets of oil so as todrive upwardly said vapor product such that it moves rapidly across thesurfaces of said sheets to promote distillation, said vapor productentraining some oil therewith; and removing said vapor product and oilentrained therewith from the top of said distillation column by pumpingsaid vapor product and entrained oil therefrom with a liquid ring vacuumpump.
 2. The method of claim 1 wherein said driving sheets stepcomprises driving said sheets in parallel with relatively close spacingtherebetween so as to form a relatively fast counter-current flow ofvapor therebetween.
 3. The method of claim 2 which further comprises thesteps of:separating said entrained oil from said vapor product; andreturning at least a portion of said separated entrained oil to saidliquid ring vacuum pump as sealant liquid.
 4. The method of claim 1which further comprises the step of exciting molecules of oil to beremoved as vapor product in said removing step by directing microwaveenergy to said molecules of oil in said distillation column.
 5. A methodof distilling a distillation product from a distillable liquidcomprising the steps of:downwardly driving at from approximately 1 to 50meters per second closely spaced parallel sheets of said distillableliquid, each sheet having a relatively narrow thickness and a relativelylarge surface, in a distillation column at distillation temperature andpressure such that a distillation vapor product is formed therefrom;upwardly driving said vapor product by forming a low pressure at the topof said distillation column above said sheets of distillable liquid suchthat said vapor product moves rapidly across the surfaces of and betweensaid sheets and entrains some of said distillable liquid therewith topromote distillation; removing said vapor product and distillable liquidentrained therewith from the top of said distillation column above saidsheets of liquid by pumping said vapor product and entrained distillableliquid therefrom with a liquid ring vacuum pump; separating saidentrained distillable liquid from said vapor product; and utilizing atleast a portion of said separated entrained distillable liquid assealant liquid in said liquid ring vacuum pump.
 6. The method of claim 5wherein said distillable liquid is oil.
 7. The method of claim 5 whereinsaid distillable liquid is edible oil.
 8. The method of claim 5 whereinsaid distillable liquid is edible oil and said distillable product iscomprised of tocopherol or fatty acids.
 9. A method of distilling two ormore distillation products from a distillable liquid comprising thesteps of:downwardly driving at from approximately 1 to 50 meters persecond closely spaced parallel sheets of said distillable liquid, eachsheet having a relatively narrow thickness and a relatively largesurface, in two or more distillation columns connected in series atdistillation temperatures and pressures such that two or moredistillation vapor products are formed therefrom; upwardly driving saidvapor products in said distillation columns by forming low pressures atthe tops of said distillation columns above said sheets of distillableliquid therein such that said vapor products move rapidly across thesurfaces of and between said sheets to promote distillation, said vaporproducts entraining some of said distillable liquid therewith; removingsaid vapor products and distillable liquid entrained therewith from thetops of said distillation columns by pumping said vapor products andentrained distillable liquid therefrom with liquid ring vacuum pumps;separating said entrained distillable liquid from said vapor products;and returning at least a portion of said separated distillable liquid tosaid liquid ring vacuum pumps for use therein as sealant liquid.
 10. Themethod of claim 9 wherein said distillable liquid is oil.
 11. The methodof claim 9 wherein said distillable liquid is edible oil and saiddistillation vapor products are comprised of tocopherol and fatty acids.12. The method of claim 11 wherein said distillation vapor products arecondensed and recovered.